This invention relates to dual lane conversion systems particularly adapted for conversion systems making easy-open can ends, although it will be understood that it could apply to presses manufacturing other types of parts.
Presses for converting ends for cans and the like are known. Presses of this general type are available from the Minster Machine Company of Minster, Ohio. U.S. Pat. No. 4,568,230 shows a general layout of a press for processing work pieces or shells into finished can ends with an opening tab attached thereto.
The presses used for the manufacture of easy-open can ends generally comprise a press bed mounted on legs which rest on the floor. Four columns or uprights or pillars are mounted on the press bed. The columns support a crown in which a main drive for the various press components is mounted. The columns also have slides or ways attached thereto for supporting a reciprocating ram. The ram carries upper tooling, which cooperates with lower tooling on the bed. The tooling defines a plurality of stations in which the shells are progressively converted into easy-open can ends. A conveyor carries the shells into and through the stations of the die tooling. The shells merely rest in openings in the conveyor. They are held in place by a vacuum box placed generally underneath the forward run of the conveyor at the area of the tooling.
The tabs are formed by tab tooling, which is supplied with strip stock by a stock feed mechanism. The tab tooling forms a tab and separates it from the strip stock, and attaches it to a can end.
While presses as generally described above are known, there remain several difficulties associated with the setup, operation and maintenance of the presses, which reduce productivity. First, it can be appreciated that the various moving parts of the press must be precisely aligned to assure production of high quality parts. Most obviously, the upper tooling which reciprocates on the ram must be precisely in alignment with the stationary lower tooling. This requires that the ram and, therefore, the columns be precisely located. Similarly, the conveyor or transfer system must cooperate with the tooling to place the work pieces or shells in the proper place for conversion by the tooling. Operation of the conveyor system is complicated by the fact that the shells must be indexed through the stations of the die tooling not only longitudinally, but also in a vertical direction to accommodate the reciprocating motion of the upper tooling. Location of the tab stock feeder mechanism further complicates the alignment problems encountered in setting up the machine.
The second difficulty with prior art presses was just eluded to, namely, the need to maintain registration of the shells as they move from one station to the next. While it is known to use a vacuum box to keep the shells from flying off the conveyor entirely, prior art vacuum boxes make no provision for the vertical motion of the upper tooling. That is, in order to move the shells longitudinally from station to station, they must be spaced from the upper and lower tooling during indexing. However, during a downstroke of the ram the shells must come into contact with the tooling in order for it to perform conversion operations. In prior vacuum boxes this vertical motion results simply by allowing flexure of the conveyor belt under the influence of the upper tools driving the shells and conveyor belt downwardly. This can lead to loss of registration of the shells on the conveyor.
A third difficulty of prior press designs is the down time caused by inconvenient access to the tooling. A primary reason for poor service access is the necessary location of the tab stock feeder mechanism adjacent or opposite the tooling. Thus, only one side of the tooling is accessible for maintenance purposes. While the tab stock feeder mechanism can be disassembled for access to the tooling, such a process is time consuming and inconvenient. The machine and its timing must be totally set up again, because once the tab stock feeder is disconnected from the drive, the necessary timing is lost.